At Children's Hospital, we are actively engaged in the development of tests to assess vision in the very young patient. The present proposal introduces a new and previously untried method to measure the Contrast Sensitivity Function (CSF) in infants and young children. The CSF provides a great deal of information about spatial vision and also provides an estimate of visual acuity. In a clinical/hospital setting, the CSF could provide information for detection and diagnosis of a neurological or visual problem, evaluate success of medical intervention and provide information about the progression of the disease. The new method for measuring the CSF is based on the measurement of Optokinetic Nystagmus (OKN) to a moving vertical grating. By systematically varying the contrast of the grating, threshold could be determined where the grating no longer elicits OKN. A CSF could be obtained by repeating this procedure for a series of gratings of different spatial frequency. Thresholds obtained by this new method will be compared to contrast thresholds as measured by more conventional methods. We plan to determine the efficacy of the OKN/CSF method by measuring CSFs in normal subjects ranging in age from 1 month to 5 years and in adults, and comparing these results to those obtained previously by other methods (i.e., preferential looking technique and visual evoked responses). In addition, in adults we plan to compare CSFs obtained with the OKN method to those obtained by the method of limits. The OKN/CSF method could, theoretically, provide a CSF in 3-to-5 minutes of testing time, and offer the clinician a valuable and rapid tool for assessment of patient status. Once perfected, we hope to apply the OKN/CSF method at Children's Hospital to evaluate a wide range of visual and neurological problems.